Power supply unit with auxiliary boost control in bootloader mode

ABSTRACT

The technology described herein is directed to a DC input power supply unit with an auxiliary boost control circuit (or controller) that facilitates continuous supply of power to a standby output load of the power supply unit in a bootloader mode. More specifically, the auxiliary boost circuit (or controller) is configured to assume control of a primary power boost stage from a primary controller in a bootloader mode so that the power supply unit can continue to supply power to the standby output with a protection function regardless of the state of the power supply unit or primary controller.

TECHNICAL FIELD

Aspects of the disclosure are related to the field of power supplyunits, and in particular, to a direct current (DC) input switched-modepower supply unit with auxiliary boost control to facilitate continuoussupply of power to a standby output load during a bootloader mode.

BACKGROUND

A switched-mode power supply (or switching power converter) is anelectronic power supply that incorporates a switching regulator toefficiently convert electrical power. Like other power supplies, aswitched-mode power supply transfers power from a direct current (DC) oralternating current (AC) source to DC loads such as, for example, apersonal computer, a server computer, a cloud computing platform, datacenter equipment, etc., while converting voltage and currentcharacteristics. Unlike linear power supplies, the pass transistor of aswitched-mode power supply continually switches between low-dissipation,full-on and full-off states, to minimize wasted energy. The voltageregulation is achieved by varying the ratio of on-to-off time (alsoreferred to as the duty cycle).

A switched-mode power supply may be utilized to supply power to a loadover a wide range. That is, relatively large amounts of power may berequired by a load in a “normal” operating mode, whereas relativelylittle power may be required by the load during a “standby” operatingmode. For example, an LCD flat-panel television receiver may require 350Watts of operating power during normal operation but may only draw anominal amount of power (e.g., 1 or 2 Watts) in a standby mode (i.e.,when the LCD flat-panel television is “turned off” in order to keepremote control circuitry active, etc.).

Switched-mode power supplies are often regulated using one or morecontrollers, e.g., microcontrollers, to, for example, maintain aconstant output voltage. Indeed, switched-mode power supplies oftenemploy digital controllers that monitor current drawn by the load andincrease or decrease the switching duty cycle as power outputrequirements change. Digital control is more popular than analog controlas there are many advantages such as, for example, flexibility, ease ofcontrol redesign and integration, reduction in the number and cost ofcomponents, etc. While digital control redesign is possible, abootloader is required to implement the redesign. A bootloader (orbootloader procedure) is a piece of code that allows user applicationcode to be updated through a communication interface such as, forexample, an I2C, a UART, etc.

Unfortunately, today's switched-mode power supplies often do not supportcontinuous supply of power to a standby output load during bootloadermode as there is no regulation for a boost stage during bootloader modeand the power supply often does not function well with low inputvoltages. Accordingly, bootloader procedures are prone to fail orotherwise cause disruptions to output loads.

SUMMARY

One or more embodiments described herein, among other benefits, solveone or more of the foregoing or other problems in the art by providingsystems, methods, and non-transitory computer readable media forcontinuously supplying power to a standby output of amicrocontroller-based switched-mode power supply unit while in abootloader mode.

In some implementations, the technology described includes a powersupply unit including an input configured to receive a DC input voltagefrom a voltage source, a main output configured to supply apredetermined DC output voltage to a load, and a standby outputconfigured to supply a nominal DC output voltage to the load. The powersupply unit further includes a filter, a boost stage circuit, a primarycontroller, a boost auxiliary circuit, a buck stage circuit, a secondarycontroller, and a bias module. The filter is coupled to the input andconfigured to reduce electromagnetic interference (EMI) in the inputvoltage. The boost stage circuit is coupled with the filter andconfigured to regulate step up of an output of the filter to a minimumthreshold voltage based on a boost regulator signal. The primarycontroller is coupled with the boost stage circuit and configured tocontrol the boost regulator signal. The boost auxiliary circuit iscoupled with the primary controller and configured to assume control ofthe boost regulator signal during the bootloader mode. The buck stagecircuit is coupled with the boost stage circuit and configured toregulate step down of an output voltage of the boost stage circuit to apredetermined DC output voltage based on a buck regulator signal. Thesecondary controller is coupled with the buck stage circuit andconfigured to control the buck regulator signal. The bias module iscoupled with the boost stage circuit and configured to regulate theoutput voltage of the boost stage circuit to a nominal DC outputvoltage.

In some implementations, the technology described includes a method ofcontinuously supplying power to a standby output of a power supply unitin a bootloader mode. The method includes receiving, by an input port ofthe power supply unit, a direct current (DC) input voltage from avoltage source, filtering, by an electromagnetic interference (EMI)filter, the input voltage, and driving, by a primary controller of thepower supply, the boost regulator signal to control regulation by aboost stage circuit. The method further includes regulating, by theboost stage circuit, step up of the filtered input voltage to a minimumthreshold voltage based on the boost regulator signal, asserting, by theprimary controller, a bootloader signal in response to receiving arequest to enter the bootloader mode, and responsive to detectingassertion of the bootloader signal, assuming, by a boost auxiliarycircuit coupled with the primary controller, control of driving theboost regulator signal to continuously supply the power to the standbyoutput of the power supply unit in the bootloader mode.

In some implementations, the technology described includes an auxiliaryboost control circuit for a low voltage direct current (LVDC) inputpower supply unit. The auxiliary boost control circuit includes meansfor monitoring for assertion of a bootloader signal in an idle state,wherein the bootloader signal indicates that a primary controller of thepower supply unit is entering a bootloader mode. The auxiliary boostcontrol circuit further includes means for transitioning the auxiliaryboost control circuit from the idle state to an auxiliary protectionstate responsive to assertion of the bootloader signal, wherein theauxiliary boost control circuit is configured to assume control of aboost regulator signal for controlling regulation of a boost stagecircuit for stepping up an input to a minimum threshold voltage.

Additional features and advantages of the present application will beset forth in the description which follows, and in part will be obviousfrom the description, or may be learned by the practice of such exampleembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features can be obtained, a more particular descriptionis set forth and will be rendered by reference to specific examplesthereof which are illustrated in the appended drawings. Understandingthat these drawings depict only typical examples and are not consideredto be limiting of its scope. Implementations will be described andexplained with additional specificity and detail through the use of theaccompanying drawings.

FIG. 1 depicts a block diagram illustrating an example power supply unitthat includes an auxiliary boost controller for assuming control of aprimary power boost stage during a bootloader mode, according to someimplementations.

FIG. 2 depicts a block diagram illustrating example components of aprimary controller in the form of a microcontroller, according to someimplementations.

FIG. 3 depicts a flow diagram illustrating an example process forentering and exiting a bootloader mode, according to someimplementations.

FIG. 4 depicts a flow diagram illustrating an example process foroperating an auxiliary boost controller to assume control of regulationof a primary power boost stage, according to some implementations.

FIG. 5 depicts a state diagram illustrating example operations of anauxiliary boost controller, according to some embodiments.

FIG. 6 depicts a signaling diagram illustrating example signalingoccurring between various components of a power supply unit during atransition from “normal” (or non-bootloader) operating mode to abootloader mode and back again, according to some implementations.

FIG. 7 depicts a flow diagram illustrating an example process forcontinuously supplying power to a standby output of a power supply unitin a bootloader mode, according to some implementations.

FIG. 8 depicts example waveforms illustrating intermediate voltagemeasurements of a power supply unit entering a bootloader mode withoutauxiliary boost control, according to some implementations.

FIGS. 9A and 9B depict example waveforms and illustrating intermediatevoltage measurements of a power supply unit entering and exitingbootloader mode with auxiliary boost control, according to someimplementations.

The drawings have not necessarily been drawn to scale. Similarly, somecomponents and/or operations may be separated into different blocks orcombined into a single block for the purposes of discussion of some ofthe embodiments of the present technology. Moreover, while thetechnology is amenable to various modifications and alternative forms,specific embodiments have been shown by way of example in the drawingsand are described in detail below. The intention, however, is not tolimit the technology to the particular embodiments described. On thecontrary, the technology is intended to cover all modifications,equivalents, and alternatives falling within the scope of the technologyas defined by the appended claims.

DETAILED DESCRIPTION

Example implementations are provided so that this disclosure will bethorough, and will fully convey the scope to persons skilled in the art.Numerous specific details are set forth such as examples of specificcomponents, devices, and methods, to provide a thorough understanding ofimplementations of the present disclosure. It will be apparent to thoseskilled in the art that specific details need not be employed, thatexample implementations may be embodied in many different forms and thatneither should be construed to limit the scope of the disclosure. Insome example implementations, well-known processes, well-known devicestructures, and well-known technologies are not described in detail.

The terminology used herein is for the purpose of describing particularexample implementations only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

Although the terms first, second, third, etc., may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,”“lower,” “above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

As noted above, switched-mode power supplies are often regulated usingone or more digital controllers, e.g., microcontrollers, to, forexample, maintain a constant output voltage. Furthermore, it isnecessary to implement a bootloader procedure in order to effectuate anyredesign of the digital control. Unfortunately, today's switched-modepower supplies often do not support continuous supply of power to astandby output load during bootloader mode as there is no regulation fora boost stage during bootloader mode and the power supply often does notfunction well with low input voltages. Accordingly, bootloaderprocedures are prone to fail or otherwise cause disruptions to outputloads.

The technology described herein is directed to a DC input power supplyunit with an auxiliary boost control circuit (or controller) thatfacilitates continuous supply of power to a standby output load of thepower supply unit in a bootloader mode. More specifically, the auxiliaryboost circuit (or controller) is configured to assume control of aprimary power boost stage from a primary controller in a bootloader modeso that the power supply unit can continue to supply power to thestandby output with a protection function regardless of the state of thepower supply unit or primary controller.

FIG. 1 depicts a block diagram illustrating an example power supply unit100 that includes an auxiliary boost controller 118 for assuming controlof a primary power boost stage 114 during a bootloader mode, accordingto some implementations. More specifically, the auxiliary boostcontroller 118 is configured to assume control of the primary powerboost stage 114 to support supplying a standby output 124 to a load (notshown) when the primary controller 116 is in a bootloader mode. As shownin the example of FIG. 1, the power supply unit 100 is a low voltage DCinput switched-mode power supply (SMPS). However, it is appreciated thatthe power supply unit 100 can be any power supply that continuouslysupports a standby output to a load in bootloader mode.

As shown in the example of FIG. 1, the power supply unit 100 comprises aboost-buck converter in a two-stage cascaded topology (boost into buck).More specifically, the initial boost stage either allows the passing ofvoltage inputs greater than a minimum threshold voltage or utilizes itsboost capabilities to increase input voltages to the minimum thresholdvoltage. The buck stage then takes the heightened (or stepped up)voltage levels from the initial boost stage and converts them to asteady predetermined output voltage.

The power supply unit 100 includes a primary power circuit 110 and asecondary power circuit 120. The primary power circuit 110 includes a DCinput 105, an electromagnetic interference (EMI) filter 112, a primarypower boost stage 114, a primary controller 116, and an auxiliary boostcontroller 118. The secondary power circuit 110 includes a bias module122, a secondary power buck stage 124, and a secondary controller 126.Other components, modules or controllers are also possible.

In operation, the power supply unit 100 receives and feeds a DC input105 to the EMI filter 112. The EMI filter 112 is configured filter DCinput 105 to acceptable predetermined levels. The problem with EMI isthat it can induce to malfunction of electronic equipment, falseactivation of protection devices or inaccurate operation of radar andtelecommunication equipment if the amount of radiated EMI does notcomply with electromagnetic compatibility standards. Accordingly,adequate filtering is necessary to guarantee quality of the power supplyunit 100. Switch-mode power supplies, inverters and in general all powerelectronics are sources of EMI. Indeed, EMI is generated by mostelectrical and electronic equipment when switching of the current takesplace. In some implementations, the EMI can take the form of conductedEMI, noise that travels through electrical conductors, wires andcomponents. The EMI can also manifest as radiated EMI which is noisethat travels through the air as magnetic fields or radio waves. Theoutput of the EMI filter 112 is fed to the primary power boost stage114.

The primary power boost stage 114 steps up (or increases) the output ofthe EMI filter 112 to the minimum threshold voltage. As shown in theexample of FIG. 1, the step up (or increase) is regulated by boostcontrol signaling 115 provided by the primary controller 116 during a“normal” (or non-bootloader) operating mode and by the auxiliary boostcontroller 118 during a bootloader mode. As discussed herein, abootloader is a piece of code which allows user application code to beupdated through a communication interface such as, for example, I2C,UART, etc. The power supply unit 100 is said to be in the bootloadermode when the primary controller 116 is performing bootloaderoperations. Thus, the boost control signaling 115 is driven by theprimary controller 116 during the “normal” (or non-bootloader) operatingmode and by the auxiliary boost controller 118 during the bootloadermode.

The primary controller 116 can be a microcontroller or any digitalcircuitry configured to monitor the output V_(bulk) of the primary powerboost stage 114 and, in turn, regulate the primary power boost stage 114via the boost control signaling 115 during the “normal” (ornon-bootloader) operating mode. The primary controller 116 providesdigital control over the primary power boost stage 114 during the“normal” (or non-bootloader) operating mode. As discussed herein,compared to analog control, there are numerous advantages to digitalcontrol including, but not limited to, flexibility, ease of controlredesign, ease of integration, components reduction, reduced componentcosts, etc. However, it is necessary to implement a bootloader procedurewhen the digital control is redesigned and primary controller 116 cannotregulate the primary power boost stage 114 when implementing thebootloader procedure, i.e., during the bootloader mode. Duringbootloader mode, the primary controller 116 asserts a bootloader signal(not shown) to indicate that the primary controller 116 is in thebootloader mode. An example illustrating operation of the primarycontroller 116 entering and then exiting bootloader mode is shown anddiscussed in greater detail with reference to FIG. 3. Furthermore, anexample primary controller 200 is shown and discussed in greater detailwith reference to FIG. 2.

The auxiliary boost controller 118 can be a microcontroller or a digitalor analog circuit configured to assume control of regulating the primarypower boost stage 114 via the boost control signaling 115 duringbootloader mode in order to continuously supply power to the standbyoutput 132. Although not shown in the example of FIG. 1, in someimplementations, the primary controller 116 and the auxiliary boostcontroller 118 each drive boost control signaling. In such instances,the boost control signaling can be tied together and fed to the primarypower boost stage 114.

In some implementations, the primary power boost stage 114 can be aDC-to-DC boost power converter (or step-up power converter) that stepsup voltage (while stepping down current) from its input (supply) to itsoutput (load). Although not illustrated in the example of FIG. 1, theprimary power boost stage 114 can be a class of switched-mode powersupply (SMPS) containing at least two semiconductors (a diode and atransistor) and at least one energy storage element: a capacitor,inductor, or the two in combination. Furthermore, to reduce voltageripple, filters made of capacitors (sometimes in combination withinductors) can be included to such a converter's output (load-sidefilter) and input (supply-side filter). The output V_(bulk) of theprimary power boost stage 114 is fed to the secondary power circuit 120.

The secondary power buck stage 124 steps down (or decreases) the outputV_(bulk) of the primary power boost stage 114 to regulate or otherwisemaintain the main output 134 to a load (not shown) as constant. As shownin the example of FIG. 1, the step down (or decrease) is regulated bybuck control signaling 127 provided by the secondary controller 126. Thesecondary controller 126 can be a microcontroller or any digitalcircuitry configured to monitor the main output 134 of the secondarypower buck stage 124 and, in turn, regulate the secondary power buckstage 124 via the buck control signaling 127 during the “normal” (ornon-bootloader) operating mode.

In some implementations, the secondary power buck stage 124 can be aDC-to-DC power converter (or step-down converter) that steps downvoltage (while stepping up current) from its input (supply) to itsoutput (load). Although not illustrated in the example of FIG. 1, thesecondary power buck stage 114 can be a class of SMPS containing atleast two semiconductors (a diode and a transistor) and at least oneenergy storage element, a capacitor, inductor, or the two incombination. However, many modern buck converters replace the diode witha second transistor for synchronous rectification. To reduce voltageripple, filters made of capacitors (sometimes in combination withinductors) can be included to such a converter's output (load-sidefilter) and input (supply-side filter).

The bias module 122 also receives the output V_(bulk) of the primarypower boost stage 114 and generates a standby output 132. The powersupply unit 100 can be utilized to supply power to a load over a widerange. For example, relatively large amounts of power may be provided toa load via the main output 134 in the “normal” operating mode, whereasrelatively very little power may be provided to the load via the standbyoutput 132 in the “standby” operating mode. As discussed above, existingswitched-mode power supplies cannot support standby output load inbootloader mode as there is no regulation for the primary power booststage 114 during bootloader mode and the bias module cannot work well inlow input voltage either. Advantageously, the auxiliary boost controller118 enables the power supply unit 100 to continuously drive (orotherwise support) the standby output 132 during the bootloader mode.

FIG. 2 depicts a block diagram illustrating example components of aprimary controller 200 in the form of a microcontroller, according tosome implementations. More specifically, the example of FIG. 2 depicts aprimary controller 200 including a detailed view of a flash memory map220 stored in memory 210, according to some implementations. The primarycontroller 200 can be primary controller 116 of FIG. 1, althoughalternative configurations are possible. As illustrated in the exampleof FIG. 2, the example components include memory 210, a communicationinterface 230, and a processing system 240. Additional or fewercomponents are possible.

In some implementations, the primary controller 200 can be amicrocontroller or other circuitry that retrieves and executes softwarefrom memory 210. The primary controller 200 may be implemented within asingle device or chip. As discussed with reference to FIG. 1, theprimary controller 200 is operatively or communicatively coupled withvarious components including an auxiliary boost controller, a primarypower boost stage, and a secondary controller.

As shown in the example of FIG. 2, the memory 210 can include programmemory (or code 212) and data memory (data 214). Primary controller 200functions discussed herein, and other circuitry and algorithmsassociated with the primary controller 200 can be implemented assoftware algorithms and may be stored as software code (e.g., in codememory 212). Similarly, real-time data and values of pre-definedconstants may be stored in one or more forms of data memory (e.g., datamemory 214). Although not shown, memory 210 includes a flash orNon-Volatile Memory (NVM). For example, the flash memory can be used tohold firmware code for the microcontroller. In such instances, on powerup, a bootloader reads the contents of the flash memory and writes it toan internal SRAM. After the firmware code is written to SRAM, theprimary controller 200 starts running from SRAM. The example of FIG. 2,the flash memory map 220 illustrates a memory allocation with abootloader function. More specifically, the flash memory map 220illustrates various sections of the flash memory including an unusedsection 131, a user application section 232, a user applicationinterrupt vector table section 233, another unused section 234, abootloader section 235, and a bootloader interrupt vector table 236.

The communication interface 230 may include communication connectionsand devices that together facilitate communication with othercommunication devices. The communication interface 230 can be anycommunication interface through which user application code can beupdated such as, for example, an I2C, a UART, etc. The processing system240 can include one or more processor cores that are configured toretrieve and execute the instructions for regulating the primary powerboost stage 114 as discussed herein.

FIG. 3 depicts a flow diagram illustrating an example process 300 forentering and exiting a bootloader mode, according to someimplementations. The example microcontroller process 300 may beperformed in various implementations by a primary controller (ormicroprocessor) such as, for example, the primary controller 116 of FIG.1 the primary controller of FIG. 2, or one or more processors, modules,engines, or components associated therewith.

To begin, at 310, the primary controller receives a request to enter abootloader mode. The request to enter the bootloader mode can beinitiated by an external system and received by a communicationinterface such as, for example, an I2C interface, a UART interface, etc.As discussed herein, the request to enter the bootloader mode includes arequest to update user application code. At 320, the primary controllerenters the bootloader mode.

At decision 330, the primary controller determines if a firmware updateis required. If a firmware update is required, at 340, the primarycontroller asserts the bootloader signal. As discussed herein, assertionof the bootloader signal can be driving the bootloader signal low. Anexample is shown and discussed with reference to FIG. 8 and FIGS. 9A and9B. However, if a firmware update is not required, at 370, the primarycontroller jumps to the user application in flash memory, e.g., seeUSER_APPLICATION_BASE_ADDRESS in the user application interrupt vectortable of flash memory of FIG. 2.

At 350, the primary controller updates firmware based on the request. At360, the primary controller de-asserts the bootloader signal. As notedabove, de-assertion of the bootloader signal can be driving (orre-driving) the bootloader signal high. Lastly, at 380, the primarycontroller exits bootloader mode and resets if necessary. For example,resetting the primary controller can return the primary controller orpower supply unit to a “normal” (or non-bootloader) operating mode.

FIG. 4 depicts a flow diagram illustrating an example process 400 foroperating an auxiliary boost controller to assume control of regulationof a primary power boost stage, according to some implementations. Theexample process 400 may be performed in various implementations by anauxiliary boost controller such as, for example, the auxiliary boostcontroller 118 of FIG. 1, or one or more processors, modules, engines,or components associated therewith.

To begin, at 410, the auxiliary boost controller monitors for assertionof a bootloader signal from a primary controller. At decision 420, theauxiliary boost controller determines if a bootloader signal has beenasserted. If a bootloader signal is not received, then the processcontinues monitoring for assertion of the bootloader signal at 410. If abootloader signal is received, at 430, the auxiliary boost controllerassumes control of regulating a primary power boost stage by, forexample, driving the boost regulator signal to regulate the step up ofthe output of the filter to a minimum threshold voltage.

At 440, the auxiliary boost controller monitors for de-assertion of thebootloader signal from the primary controller. At decision 450, theauxiliary boost controller determines if the bootloader signal isde-asserted. If the bootloader signal is de-asserted, at 460, theauxiliary boost controller releases control of the bootloader signal. Asdiscussed herein, the primary controller can then re-assume control ofthe bootloader signal. Although not shown, in some implementations, theprocess then returns to monitoring for assertion of the bootloadersignal from the primary controller at 410. If the bootloader signal isnot de-asserted at decision 450, the process returns to monitoring forde-assertion of the bootloader signal at 440.

FIG. 5 depicts a state diagram 500 illustrating example operations of anauxiliary boost controller, according to some embodiments. As shown inthe example of FIG. 5, the state diagram 500 includes states 510, 520,530 and 540, entry actions 522, 532 and 542, and transition conditions515, 525, 535, 545, 536, and 546. The example state operations andtransitions shown in state diagram 500 may be performed in variousembodiments by an auxiliary boost controller such as, for example, theauxiliary boost controller 118 of FIG. 1, or one or more processors,modules, engines, or components associated therewith. Additional orfewer states, entry actions and transition conditions are possible.

The auxiliary boost controller is initially in an off state 510. Asdiscussed herein, during the off state 510, all components of the powersupply unit (including the auxiliary boost controller) are disabled.Powering on the power supply unit acts as transition condition 515transitioning the auxiliary boost controller from the off state 510 toan idle state 520. Upon entering the idle state 520, entry action 522 isperformed by the auxiliary boost controller. As shown in the example ofFIG. 5, entry action 522 includes monitoring for assertion of abootloader signal. As discussed herein, the power supply unit 100 issaid to be in the bootloader mode when the primary controller 116 isperforming bootloader operations. A bootloader is a piece of code whichallows user application code to be updated through a communicationinterface such as, for example, I2C, UART, etc.

While operating in the idle state 520, detecting an indication that thebootloader signal is asserted acts as transition condition 525transitioning the auxiliary boost controller from the idle state 520 toan auxiliary protection state 530. As discussed herein, primarycontroller asserts a bootloader signal to indicate that the primarycontroller is in the bootloader mode. Upon entering the auxiliaryprotection state 530, entry action 532 is performed by the auxiliaryboost controller. As shown in the example of FIG. 5, entry action 532includes assuming control of the primary power boost stage. Although notshown, entry action 532 also includes monitoring for occurrence of afault.

In the auxiliary protection state 530, detecting the occurrence of afault acts as transition condition 535 transitioning the auxiliary boostcontroller from the auxiliary protection state 530 to a fault state 540.Upon entering the fault state 540, entry action 542 is performed by theauxiliary boost controller. As shown in the example of FIG. 5, entryaction 542 includes performing one or more fault operations. During thefault state 540, detecting the occurrence of a reset acts as transitioncondition 546 transitioning the auxiliary boost controller from thefault state 540 back to the idle state 520. Furthermore, the occurrenceof a power off event acts as transition condition 545 transitioning theauxiliary boost controller from any state to the off state 510.

FIG. 6 depicts a signaling diagram 600 illustrating example signalingoccurring between various components of a power supply unit during atransition from “normal” (or non-bootloader) operating mode to abootloader mode and back again, according to some implementations. Theprimary controller, the auxiliary boost, and the primary power booststage can be the primary controller 116, the auxiliary boost 118, andthe primary power boost stage 114 of FIG. 1, although alternativeconfigurations are possible.

Initially, the primary controller asserts drive boost regulatorsignaling to control the regulation of the primary power boost state.When a bootloader request is received, the primary controller de-assertsthe drive boost regulator signaling and asserts the bootloader signal.The bootloader signal is received by the auxiliary boost control which,in turn, assumes control of the boost stage until the bootloader signalis de-asserted. When the bootloader signal is de-asserted, the auxiliaryboost released control of the boost stage by de-asserting the driveboost regulator signaling. The primary controller then resumes controlof the boost stage by re-asserting the drive boost regulator signaling.

FIG. 7 depicts a flow diagram illustrating an example process 700 forcontinuously supplying power to a standby output of a power supply unitin a bootloader mode, according to some implementations. The exampleprocess 700 may be performed in various implementations by a powersupply unit such as, for example, the power supply unit 100 of FIG. 1,or one or more processors, modules, engines, or components associatedtherewith.

To begin, at 710, the power supply unit receives a DC input voltage froma voltage source. At 720, the power supply unit filters the DC input forthe EMI. At 730, the power supply unit drives the boost regulator signalto control regulation by a boost stage circuit. At decision 740, thepower supply unit determines if a bootloader signal is asserted. If not,the process returns to step 710. Otherwise, at 750, the power supplyunit assumes control of driving the boost regulator signal tocontinuously supply power to the standby output of the power supply unitin bootloader mode. At decision 760, the power supply unit determines ifthe bootloader signal is de-asserted. If not, the process returns tostep 710. Otherwise, at 770, the power supply unit releases control ofdriving the boost regulator signal.

FIG. 8 depicts example waveforms 800 illustrating intermediate voltagemeasurements of a power supply unit entering a bootloader mode withoutauxiliary boost control, according to some implementations. Morespecifically, as shown in the example of FIG. 8, if the power supplyunit does not have an auxiliary boost control then the bootloaderprocedure can fail as the output of the primary power boost stage(V_(bulk)) and the standby output (V_(AUX)) are out of regulation.

FIGS. 9A and 9B depict example waveforms 900A and 900B illustratingintermediate voltage measurements of a power supply unit entering andexiting bootloader mode with auxiliary boost control, according to someimplementations. More specifically, the auxiliary boost control can beprovided by an auxiliary boost controller such as, for example,auxiliary boost controller 118 of FIG. 1. As shown in the examples ofFIGS. 9A and 9B, the standby output (V_(AUX)) is well-regulated enteringand exiting the bootloader mode.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

The included descriptions and figures depict specific embodiments toteach those skilled in the art how to make and use the best mode. Forthe purpose of teaching inventive principles, some conventional aspectshave been simplified or omitted. Those skilled in the art willappreciate variations from these embodiments that fall within the scopeof the disclosure. Those skilled in the art will also appreciate thatthe features described above may be combined in various ways to formmultiple embodiments. As a result, the invention is not limited to thespecific embodiments described above, but only by the claims and theirequivalents.

What is claimed is:
 1. A power supply unit, comprising: an inputconfigured to receive a direct current (DC) input voltage from a voltagesource; a filter coupled to the input and configured to reduceelectromagnetic interference (EMI) in the input voltage; a boost stagecircuit coupled with the filter and configured to regulate step up of anoutput of the filter to a minimum threshold voltage based on a boostregulator signal; a primary controller coupled with the boost stagecircuit and configured to control the boost regulator signal; a boostauxiliary circuit coupled with the primary controller and configured toassume control of the boost regulator signal during a bootloader mode; abuck stage circuit coupled with the boost stage circuit and configuredto regulate step down of an output voltage of the boost stage circuit toa predetermined DC output voltage based on a buck regulator signal; asecondary controller coupled with the buck stage circuit and configuredto control the buck regulator signal; a bias module coupled with theboost stage circuit and configured to regulate the output voltage of theboost stage circuit to a nominal DC output voltage; a main outputconfigured to supply the predetermined DC output voltage to a load; anda standby output configured to supply the nominal DC output voltage tothe load.
 2. The power supply unit of claim 1, wherein the boost stagecircuit comprises a boost stage configured to pass the output of thefilter when the output of the filter is greater than the minimumthreshold voltage and increase the output of the filter to the minimumthreshold voltage when the output of the filter is less than the minimumthreshold voltage.
 3. The power supply unit of claim 1, wherein theboost auxiliary circuit is further configured to maintain an idle statewhen the power supply unit is not in the bootloader mode and enter thebootloader mode in response to receiving a bootloader signal initiatedby the primary controller.
 4. The power supply unit of claim 3, whereinthe boost auxiliary circuit is configured to assume control of the boostregulator signal during the bootloader mode by driving the boostregulator signal to regulate the step up of the output of the filter tothe minimum threshold voltage.
 5. The power supply unit of claim 4,wherein the bias module is further configured to continuously regulatethe output voltage of the boost stage circuit to the nominal DC outputvoltage during the bootloader mode.
 6. The power supply unit of claim 4,wherein the primary controller is further configured to assert thebootloader signal in response to receiving a request to enter thebootloader mode.
 7. The power supply unit of claim 6, wherein theprimary controller is further configured to perform a firmware update inresponse to the request and de-assert the bootloader signal uponcompletion of the firmware update.
 8. The power supply unit of claim 1,wherein the boost auxiliary circuit is further configured to monitor foroccurrence of a fault during the bootloader mode.
 9. The power supplyunit of claim 1, wherein the boost auxiliary circuit comprises amicrocontroller or analog circuitry.
 10. The power supply unit of claim1, wherein the boost stage circuit comprises a switching regulatorcircuit.
 11. A method of continuously supplying power to a standbyoutput of a power supply unit in a bootloader mode, the methodcomprising: receiving, by an input port of the power supply unit, adirect current (DC) input voltage from a voltage source; filtering, byan electromagnetic interference (EMI) filter, the DC input voltage;driving, by a primary controller of the power supply unit, a boostregulator signal to control regulation by a boost stage circuit;regulating, by the boost stage circuit, step up of the filtered inputvoltage to a minimum threshold voltage based on the boost regulatorsignal; asserting, by the primary controller, a bootloader signal inresponse to receiving a request to enter the bootloader mode; andresponsive to detecting assertion of the bootloader signal, assuming, bya boost auxiliary circuit coupled with the primary controller, controlof driving the boost regulator signal to continuously supply the powerto the standby output of the power supply unit in the bootloader mode.12. The method of claim 11, further comprising: prior to assumingcontrol of the driving of the boost regulator signal, monitoring, by theboost auxiliary circuit, for the assertion of bootloader signal.
 13. Themethod of claim 11, further comprising: responsive to assuming controlof the driving of the boost regulator signal, monitoring, by the boostauxiliary circuit, for de-assertion of the bootloader signal.
 14. Themethod of claim 13, further comprising: responsive to detectingde-assertion of the bootloader signal, releasing, by the boost auxiliarycircuit, control of driving the boost regulator signal; and responsiveto releasing control of the boost regulator signal, resuming, by theprimary controller of the power supply, control of driving the boostregulator signal to maintain regulation by the boost stage circuit. 15.The method of claim 13, wherein the boost stage circuit comprises aswitching regulator circuit.
 16. The method of claim 13, wherein theboost stage circuit comprises a boost stage configured to pass an outputof the EMI filter when the output of the EMI filter is greater than theminimum threshold voltage and increase the output of the EMI filter tothe minimum threshold voltage when the output of the EMI filter is lessthan the minimum threshold voltage.
 17. An auxiliary boost controlcircuit for a low voltage direct current (LVDC) input power supply unit,the auxiliary boost control circuit comprising: means for monitoring forassertion of a bootloader signal in an idle state, wherein thebootloader signal indicates that a primary controller of the LVDC inputpower supply unit is entering a bootloader mode; and means fortransitioning the auxiliary boost control circuit from the idle state toan auxiliary protection state responsive to assertion of the bootloadersignal, wherein the auxiliary boost control circuit is configured toassume control of a boost regulator signal for controlling regulation ofa boost stage circuit for stepping up an input to a minimum thresholdvoltage.
 18. The auxiliary boost control circuit of claim 17, furthercomprising: means for monitoring for de-assertion of the bootloadersignal in the auxiliary protection state; and means for transitioningthe auxiliary boost control circuit from the auxiliary protection stateback to the idle state responsive to the de-assertion of the bootloadersignal.
 19. The auxiliary boost control circuit of claim 17, furthercomprising: means for monitoring for a fault condition in the auxiliaryprotection state; and means for transitioning the auxiliary boostcontrol circuit from the auxiliary protection state to a fault stateresponsive to the fault condition.
 20. The auxiliary boost controlcircuit of claim 19, wherein the fault condition comprises one or moreof an overcurrent protection fault or an overvoltage protection fault.